WASHINGTON  A Supreme Court ruling Monday that the Environmental Protection Agency can regulate carbon dioxide and other greenhouse gases galvanized groups that have long sought to limit emissions from new cars and trucks.

The 5-4 decision in the court's first-ever case on global warming forces the EPA to re-evaluate whether its regulation of tailpipe emissions should include carbon dioxide. It also adds momentum to congressional and state efforts to address climate change.

The opinion could ultimately affect whether automakers are required to build higher-mileage vehicles that emit less carbon dioxide. The court emphasized the link between increased concentrations of carbon dioxide in the atmosphere and rising temperatures.

"This decision puts the wind at our back," says Sen. Barbara Boxer, D-Calif., chairman of the Senate Committee on Environment and Public Works. She said the panel will work toward comprehensive legislation to reduce heat-trapping gases as it pushes for EPA regulation. She says she will call EPA officials before the committee this month.

The Alliance of Automobile Manufacturers said it also will turn to Congress. "There needs to be a national, federal, economy-wide approach to addressing greenhouse gases," said Dave McCurdy, president of the alliance.

The decision, written by liberal Justice John Paul Stevens and secured by a key fifth vote from moderate conservative Justice Anthony Kennedy, said "the harms associated with climate change are serious and well recognized," including the loss of coastal land to rising sea levels.

"Today's ruling is a watershed moment in the fight against global warming," said Carl Pope of the Sierra Club, which was among the groups that joined 12 states challenging the EPA.

The case began when California, which has adopted the nation's toughest emissions standards, Massachusetts and 10 other states claimed the EPA had abdicated its responsibility under the Clean Air Act to regulate carbon dioxide and other greenhouse gases. The EPA said it lacked such authority under the act and asserted that, even if it had such power, it would not use it because of domestic and foreign policy concerns.

The court said the EPA must give scientific grounds, not policy or political reasons. "The EPA has offered no reasoned explanation for its refusal to decide whether greenhouse gases cause or contribute to climate change," Stevens wrote.

Dissenting were Chief Justice John Roberts and Antonin Scalia, Clarence Thomas and Samuel Alito. They said the states lacked "standing" to sue because they failed to show they would be harmed by the EPA's policy on emissions. Roberts said the majority "ignores the complexities of global warming."

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